1. Field of the Invention
The invention relates to casters, and is in particular concerned with twin-wheel casters embodying externally-operable brake means comprising a brake member which engages the caster wheels internally to lock them against rotation.
2. Description of the Prior Art
Various constructions of braked twin-wheel caster have been proposed, with a projecting operating member mounted in the body of the caster and which is either axially movable (as for example in UK Patents Nos. 2,054,070 and 2,074,024) or is rockable or pivotally mounted (as for example in UK Patents Nos. 2,074,024 and 2,090,637). All these constructions suffer from the disadvantage that separate elements of the brake means have to be fitted from the inner side of the caster body prior to fitting the wheels, these elements being at least the brake member which engages the wheels and commonly also other elements such as a return spring. This considerably complicates the assembly of the caster as compared with a similar `non-braked` caster without a braking mechanism, particularly when both "braked" and "non-braked" casters have to be assembled on the same assembly line.
Prior constructions in which locking projections of a lever engage between radial ribs or webs in identical wheels possess the disadvantage that an applied moment tending to rotate a locked wheel can apply a force to the lever which may displace it from the locking position.
The prior UK Pat. No. 2,090,637 referred to discloses a braked caster with a two-component member in the form of a pivotally-mounted lever which projects from the body and provides both the locking member and the operating member. A locking pin which projects laterally adjacent the inner end of the lever engages for locking purposes between internal ribs or webs in the wheels. This construction reduces the number of separate parts required and the main portion of the lever can be fitted from outside the caster, but it is still necessary to fit both the locking pin and a pivot pin mounting the lever from within the body, and thus before both caster wheels have been fitted.